Polio strains detected in Cape Town sewage; officials say South Africa remains polio-free

The National Institute for Communicable Diseases (NICD) has detected two polio virus strains VDPV3 and nOPV2-L in wastewater sampled from a treatment plant in Cape Town, health authorities said.

What officials found and what it means

Department of Health spokesperson Foster Mohale said the detections were identified through the NICD’s routine environmental and wastewater testing, which analyses municipal sewage and water resources to track disease across populations.

“These detections are called vaccine events because no actual cases of the virus have been detected in a human being,”

Mohale said, adding that the findings do not indicate a clinical outbreak.

Mohale said:

“This does not translate to an outbreak.”

Public health response and context

Mohale described the NICD surveillance as a proactive tool to detect emerging outbreaks and viral variants before clinical cases appear. He said that while these events require a public health response, they are not high risk and no additional vaccination campaign is required.

The department also said the viruses detected in wastewater are likely from imported cases among people vaccinated with vaccines different from those used in South Africa.

South Africa’s polio status and expert comments

South Africa was officially certified polio-free by the World Health Organization in September 2019, the department noted.

Water scientist Ayesha Laher said the presence of polio in wastewater indicates there were people carrying the virus in the community and described that as a health risk. She also commented on the poor state of some wastewater treatment infrastructure but said it had no connection to the polio detection.

Separately, Wiida Fourie-Basson, a spokesperson for the University of Stellenbosch Faculty of Science, noted that researchers found genetic material from two major bacterial groups with high-risk resistance profiles in wastewater samples from the City of Tshwane.

Key points

• NICD detected VDPV3 and nOPV2-L in wastewater from a Cape Town treatment plant.
• No human polio cases have been detected; authorities classify the findings as vaccine events.
• Health officials say detections do not constitute an outbreak and no extra vaccination campaign is required.
• South Africa was certified polio-free in September 2019.